Various systems and methods exist to provide radiation therapy treatment of tumorous tissue with high-energy radiation. While some patient conditions require whole body radiation treatments, many forms of radiation treatment benefit from the ability to accurately control the amount, location and distribution of radiation within a patient's body. Such control often includes applying various levels of radiation to various areas of the tumorous region. For example, in some instances it is desirable to apply a greater dosage of radiation to one portion of a tumorous region than another. As another example, in some instances it is desirable to minimize the dosage of radiation to non tumorous regions where radiation may have deleterious effects. Due to a variety of contributing factors, achieving accurate control of the amount, location and distribution of radiation within the patient's body can be difficult. Among these factors are movement in the patient's body, changes in organ or inter organ structure or composition, and changes in the relative position of a patient's organs.
Prior to a radiation therapy, the patient undergoes an imaging procedure to determine the exact size, shape and location of the tumorous region. In a radiation treatment session, the patient is subjected to radiation from an accelerator that emits a beam of radiation energy collimated and oriented to enter the patient's body from a particular angle. Varying the intensity and the entry angle of the incident radiation beam allows a radiation specialist to generate a radiation dose volume that corresponds to the size, shape, and location of the tumorous region.
Several factors may prevent optimal radiation exposure to the tumorous region and minimal radiation exposure of the healthy tissue regions. For example, minor changes in patient's position from the imaging device to the treatment device may radically alter the position of the tumorous region or organ. In existing procedures, the patient is generally placed on a first patient support when the imaging device is used to obtain images of the patient. After the imaging session, the patient is then moved to a second patient support where the patient can be treated in a treatment session. As a result of moving the patient to different supports, the position and/or the shape of the target tissue within the patient may change. As such, it may be desirable to provide a radiation system that allows a transportation distance for the patient between the diagnostic device and the treatment device to be minimized, or at least reduced, thereby reducing the chance of having the target tissue change position and/or shape.
In some radiation procedures, such as a Positron emission tomography and computed tomography (PET-CT), a patient may be positioned between two diagnostic devices. PET detects photons generated through positron-electron annihilation of positrons from a radioactive tracer placed in the object, e.g., patient, to be imaged, and analyzes the photon energy and trajectory to generate tomographic images of the patient. PET images may be used to identify areas where a tumor is actively growing. However, due to attenuation effect in PET procedures, PET images tend to be blurry. As such, it may be desirable to obtain information about an anatomy, such as a density of tissue, that is being imaged, and use such information to correct attenuation effect in PET imaging. CT imaging may be used to obtain density information, and therefore, may be used to correct attenuation effect in PET images. In existing PET-CT procedures, the patient is generally placed in a first operative position associated with the PET device, and a PET imaging procedure is performed to obtain PET images of the patient. After the PET imaging session, the patient may be moved to a second operative position associated with the CT device, and a CT imaging procedure is performed to obtain CT or x-ray images of the patient. The CT image data obtained using the CT device may then be used to perform attenuation correction for the PET images obtained using the PET device. As a result of moving the patient between the PET and CT devices, the position and/or the shape of the target tissue within the patient may change. In some cases, the PET and CT devices may be combined in a single machine. However, in such systems, the machine can only perform low energy imaging of the patient, and is not capable of providing treatment to the patient.